This invention is directed to tire processing equipment and, more particularly, to an electronic circuit for use in such equipment. Specifically, this invention relates to an electronic circuit which is responsive to the rate of change in amplitude of an analog electrical signal that is representative, for example, of the surface configuration of a tire to detect when the rate of change in amplitude equals or exceeds a predetermined rate.
In the tire grinding machine of Hofelt, Jr. et al., "Means for Correcting Non-Uniformity in Tires," U.S. Pat. No. 3,724,137 (Apr. 3, 1973), wherein such an electronic circuit is not used, a sensor (numeral 87 in FIG. 3 and numeral 152 in FIG. 6) is employed to transduce the radial dimension of a tire. The output of the sensor controls a servo system to position grinders which correct force variations and/or eccentricity of a tire of the bias, radial, or wide-oval type.
A problem arises, however, if the output of the sensor in the Hofelt, Jr. et al. tire grinding machine is employed to control a servo system to position grinders to correct a lugtype tire, that is, a tire with large cleats. Often there is a relatively deep groove between lugs on a lug-type tire. The sensor does not distinguish lugs on a lug-type tire from abnormal variations in the radial dimension which occur in the road-contacting surface of the lugs on the tire. If the output of the sensor in the Hofelt, et al. tire grinding machine were used to control a servo system to position grinders to correct a lug-type tire, grinders might grind off lugs and destroy the tire.
In order to remedy this situation, an electronic circuit which is responsive to the rate of change in amplitude of the analog electrical signal from the sensor could be used to mask that portion of the analog electrical signal representative of grooves on a lug-type tire. Hence, the output of the electronic circuit could control a servo system to position grinders without grinding off lugs so that the tire grinding machine could be used to correct force variations and/or eccentricity in a lug-type tire.
Such an electronic circuit could also be used in combination with any other type of transducer which converts a physical condition into an analog electrical signal. A thermocouple to provide an analog electrical signal which is representative of a temperature, for example, could be used in combination with the electronic circuit to monitor a cooling system. If the rate of change in temperature were to equal or exceed a preselected limit, the electronic circuit could operate apparatus to indicate an abnormality.
An electronic circuit which is responsive to the rate of change in amplitude of an analog electrical signal also has many other applications. Such an electronic circuit could be used to detect, for example, an overvoltage or overcurrent transient condition on a power line. If the rate of change in amplitude of the voltage or current on the power line were to equal or exceed a preselected limit, the electronic circuit could operate protective devices so that equipment, such as motors that are connected to the power line, would not be damaged.
One objective of this invention is to provide an electronic circuit which is responsive to the rate of change in amplitude of an analog electrical signal to detect when the rate of change in amplitude equals or exceeds a predetermined limit.
A further objective of this invention is to provide an electronic circuit of the above type which is highly stable and yet which is sensitive to the rate of change in amplitude of an analog electrical signal.
An additional objective of this invention is to provide an electronic circuit to detect when the rate of change in amplitude of an analog electrical signal equals or exceeds a predetermined limit, wherein the predetermined limit may be adjustably preset.
Another objective of the present invention is to provide an electronic circuit to detect when the rate of change in amplitude of an analog electrical signal equals or exceeds a predetermined limit, wherein the electronic circuit is automatically reset after abatement of the condition in which the rate of change in amplitude equals or exceeds the predetermined limit.
A further objective of the present invention is to provide an electronic circuit to detect when the rate of change in amplitude of an analog electrical signal equals or exceeds a predetermined limit, wherein the electronic circuit has as an output the amplitude of the analog electrical signal at the time that the rate of change in amplitude equals or exceeds a predetermined limit until reset occurs.
An additional objective of the present invention is to provide an electronic circuit of the above type which is specially adapted for use in a tire grinding machine for lugtype tires, such as snow and truck tires.